Like other cells, leukocytes have the cellular skeleton comprising microtubules, actine, myosine, and intermediate filaments. Elements of the cellular skeleton are connected with receptors on the plasma membrane surface and determine the distribution density of these receptors. There is functional relationship between microtubules and actine filaments, in particular, microtubules determine uniform distribution of actine filaments in the cell cytoplasm. The basic principle of functioning of the cellular skeleton consists of the process of polymerization and reversible depolymerization of proteins forming components of the cellular skeleton. These processes are regulated by Ca2+, calmoduline, as well as by the ratio of cyclic adenosine monophosphate and guanidine monophosphate in the cell. The cellular skeleton determines the most important functions of leukocytes: their mobility, binding and absorption of various substances, processes of degranulation, fusion of granules with phagocytic vacuole. Cellular skeleton defects are accompanied by recurrent bacterial infections. Several such defects are known: leukocyte actine dysfunction syndrome, Chediak-Higashi syndrome, syndrome with marked increase in the content of cGMP and microtubules in leukocytes. In these syndromes, the therapeutic effect is achieved with the substances which regulate the level of cyclic nucleotides in leukocytes, among them large doses of ascorbic acid.